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A007869 Number of complementary pairs of graphs on n nodes. Also number of unlabeled graphs with n nodes and an even number of edges. 12
1, 1, 2, 6, 18, 78, 522, 6178, 137352, 6002584, 509498932, 82545586656, 25251015686776, 14527077828617744, 15713242984902154384, 32000507852263779299344, 122967932076766466347469888, 893788862572805850273939095424, 12318904626562502262191503745716384 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..50

P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

Nevena Francetić, Sarada Herke, Ian M. Wanless, Parity of Sets of Mutually Orthogonal Latin Squares, arXiv:1703.04764 [math.CO], 2017. See Section 4.1.

Ferenc Szöllosi, The two-distance sets in dimension four, arXiv:1806.07861 [math.MG], 2018. See Table 1.

FORMULA

Average of A000088 and A000171.

MATHEMATICA

Needs["Combinatorica`"]; Table[Total[Table[NumberOfGraphs[n, m], {m, 0, Binomial[n, 2], 2}]], {n, 1, 15}]  (* Geoffrey Critzer, Oct 20 2012; modified by Harvey P. Dale, Aug 08 2013 *)

CROSSREFS

Cf. A000088, A000171.

Cf. A054960 for graphs with an odd number of edges.

Sequence in context: A113844 A266858 A141580 * A263915 A144557 A273001

Adjacent sequences:  A007866 A007867 A007868 * A007870 A007871 A007872

KEYWORD

nonn,nice

AUTHOR

Peter J. Cameron

EXTENSIONS

More terms from Vladeta Jovovic, Jul 19 2000

Terms a(18) and beyond from Andrew Howroyd, Sep 17 2018

STATUS

approved

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Last modified November 18 17:49 EST 2018. Contains 317323 sequences. (Running on oeis4.)